A replicated study in North Carolina, USA (Stanback & Dervan 2001), found that eastern bluebirds Sialis sialis preferentially selected cleaned nest boxes over uncleaned boxes, with 71% of 45 pairs switching from a previously-used box to an unused one. However, if successful nest boxes were cleaned then 75% of 32 pairs remained in the same box, rather than moving to an identical, cleaned box.